Japheth first appears in the Book of Genesis as one of the three sons of Noah, saved through the Ark. They are always in the order "Shem, Ham, and Japheth" when all three are listed (Genesis 5:32, 9:18 and 10:1),[6] but Genesis 9:24 calls Ham the youngest,[6] and Genesis 10:21 refers ambiguously to Shem as "brother of Japheth the elder," which could mean that either is the eldest.[7] Most modern writers accept Shem-Ham-Japheth as reflecting birth order, but this is not always the case: Moses and Rachel also appear at the head of such lists despite explicit descriptions of them as younger siblings.[8]

Following the Flood he features in the story of Noah's drunkenness. Ham sees Noah drunk and naked in his tent and tells his brothers, who then cover their father with a cloak while avoiding the sight; when Noah awakes he curses Canaan, the son of Ham, and blesses Shem and Japheth: "Blessed be the Lord God of Shem and may Canaan be his slave; and may God enlarge Japheth and may he dwell in the tents of Shem, and may Canaan be his slave!” (Genesis 9:20-27).

Chapter 10 of Genesis, the Table of Nations, tells how the entire Earth was populated by the sons of Noah following the Flood, beginning with the descendants of Japheth:

The Book of Genesis is the first of the five books of the Torah, that accounts of Israel's origins as a people. Scholars increasingly see this as a product of the Achaemenid Empire (probably 450-350 BCE), although some would place its production in the Hellenistic period (333-164 BCE) or even the Hasmonean dynasty (140–37 BCE).[9] The story of Japheth and his brothers may be even more recent: almost none of the persons, places and stories in the first eleven chapters of Genesis (called the Primeval history) are ever mentioned anywhere else in the Bible, leading scholars to suppose that the history is a late composition, attached to Genesis to serve as an introduction to that book and to the Torah.[10][11]

Japheth (in Hebrew, Yaphet) is a transliteration of the Greek Iapetos, the ancestor of the Hellenic peoples.[12][13] His sons and grandsons associate him with the geographic area of the eastern Mediterranean and Asia - Ionia/Javan, Rhodes/Rodanim, Cyprus/Kittim, and other points in the region of Greece and Asia Minor - approximating to one of the three kingdoms into which the generals of Alexander the Great divided his empire on his death (the descendants of Shem and Ham respectively correspond to the other two, those of the Ptolemies and Seleucids). [13][14] As the point of the "blessing of Japheth" seems to be that Japheth (a Greek-descended people) and Shem (the Israelites) would rule jointly over Canaan (Palestine). From the 19th century until the late 20th century it was usual to see Japheth as a reference to the Philistines, who shared dominion over Canaan during the pre-monarchic and early monarchic period of Israel's history.[15] This view accorded with earlier understanding of the origin of the Book of Genesis, which was seen as having been composed in stages beginning with the time of Solomon, when the Philistines still existed (they vanish from history after the Babylonian conquest of Canaan). However, Genesis 10:14 identifies their ancestor as Ham rather than Japheth.[12]

Japhet, the son of Noah, had seven sons: they inhabited so, that, beginning at the mountains Taurus and Amanus, they proceeded along Asia, as far as the river Tanais (Don), and along Europe to Cadiz; and settling themselves on the lands which they light upon, which none had inhabited before, they called the nations by their own names.

Josephus subsequently detailed the nations supposed to have descended from the seven sons of Japheth.

The "Book of Jasher", published by Talmudic rabbis in the 17th century, provides some new names for Japheth's grandchildren not found in the Bible, and provided a much more detailed genealogy (see Japhetic).

In the seventh century, Isidore of Seville published his noted history, in which he traces the origins of most of the nations of Europe back to Japheth.[2] Scholars in almost every European nation continued to repeat and develop Saint Isidore's assertion of descent from Noah through Japheth into the nineteenth century.[4]

In the Polish tradition of Sarmatism, the Sarmatians were said to be descended from Japheth, son of Noah, enabling the Polish nobility to imagine themselves able to trace their ancestry directly to Noah.[4]

In Scotland, histories tracing the Scottish people to Japheth were published as late as George Chalmers' well-received Caledonia, published in 3 volumes from 1807 to 1824.[16]

Japheth is not mentioned by name in the Qur'an but is referred to indirectly in the narrative of Noah (7:64, 10:73, 11:40, 23:27, 26:119). Muslimexegesis, however, names all of Noah's sons, and these include Japheth.[17] In identifying Japheth's descendants, Muslim exegesis more-or-less agrees with the Biblical traditions.[18] He is usually regarded as the ancestor of the Gog and Magog tribes, and, at times, of the Turks, Khazars, and Slavs. Some traditions narrated that 36 languages of the world could be traced back to Japheth.[19]